1. Field of the Invention
The present invention relates to an improvement in a caster with an installation base mounted on the leg or bottom of various machines and instruments such as press machines to facilitate movement, installation, vibration-damping and stabilization of the machine or instrument and which can adjust a level of the machine or instrument.
2. Description of the Prior Art
A caster with an installation base has been heretofore known from, for example, U.S. Pat. No. 3,602,464 and the like filed by the present inventor. This caster comprises a wheel for moving a machine or instrument, and an installation base (including a vibration damper) for installing into the moved machine or instrument in a stabilized manner and for buffering against vibration of the machine or instrument itself or vibration from outside.
FIG. 14 corresponds to FIG. 3 of U.S. Pat. No. 3,602,464 and is a sectional view showing an example of the aforementioned prior art caster. Reference numeral 1 denotes a mounting nut secured to the leg or bottom of a machine or instrument, the nut being provided in the center thereof with a threaded hole 2 with which a mounting bolt (not shown) is threadedly engaged. An angularly formed handle 3 is adapted to vertically move a vibration-damper 4 made of synthetic rubber, synthetic resin or the like. A frame 5 is rotatably mounted on the mounting nut 1 through a thrust cover which will be described later, and a single wheel or movement wheel 6 is supported on the frame 5.
The mounting nut is internally formed with an annular groove 7, which receives an upper end of a thrust cover 10 rotatably held by steel ball bearings 8 and 9. The thrust cover 10 and the steel ball bearings 8 and 9 are supported by a thrust washer 11 secured to the mounting nut 1. The lower end of the thrust cover 10 is arranged in the form of a collar and welded to the upper end of the frame 5. The handle 3 arranged externally of the thrust cover 10 is supported with the bottom thereof placed on the collar-like lower end of the thrust cover 10. A gear portion 12 is provided on the inner peripheral surface of the handle 3. The frame 5 is formed with a cylindrical portion 13 into which is fitted the vibration damper 4 and a parallel portion 15 onto which the wheel 6 is mounted by a shaft 14.
A gear stopper 16 is fitted on the frame 5. In this gear stopper 16, a hole is provided at a position on one side from a center 17 of the frame 5, and an adjustment bolt 18 extends through the hole. A pinion gear 19 is fixed integrally and rotatably to the upper portion of the adjustment bolt 18, a part of which is meshed with a gear portion 12 of the handle 3 passing through a window portion of the thrust cover 10. A gear thrust 20 is provided upwardly of the pinion gear 19. The vibration damper 4 is formed to be fitted in the inner wall of the cylindrical portion 13 and mounted on an adjustment nut 21 threadedly engaged with the adjustment bolt 18.
At least three of the above-described casters with installation base are mounted on the legs or bottom of the machine or instrument. In the prior art structure shown in FIG. 14, the wheel 6 is in contact with a ground or an installation surface (not shown) of the floor or the like. By pushing the machine or instrument in the desired direction, the wheel 6 can be rolled and moved in the desired direction. To change the desired direction of movement, the direction for pushing the machine or instrument is changed. The resistance of the wheel 6 acts on the frame 5 and the thrust cover 10, whereby the thrust cover 10 is rotated between the ball bearings 8 and 9. Therefore, the direction of the frame 5 and the wheel 6 is changed to the direction of movement.
Where the machine or instrument is installed in the desired position, the frame 5 is held so that the frame may not be rotated, and the handle 3 may be rotated in a fixed direction. When the adjustment bolt 18 is rotated through the pinion gear 19 by the rotation of the handle 3, the vibration damper 4 and the adjustment nut 21 are locked by the frame 5. Therefore, the nut 21 descends along the adjustment bolt 18. If the vibration damper 4 is further allowed to move down even after the lower end of the vibration damper 4 has contacted the installation surface, the wheel 6 moves away from the floor or ground surface and ascends.
As described above, in the prior art example shown in FIG. 14, the movement wheel 6 is levitated to above the installation surface by rotating the handle 3, and at the same time, the vibration damper 4 is interposed between the machine or instrument and the ground or floor surface.
However, in the above-described prior art, constituent parts such as the pinion gear 19, adjustment bolt 18 and adjustment nut 21 for converting the rotational movement of the handle 3 into the vertical movement of the vibration damper 4 are absolutely necessary. This prior art necessity creates a problem in that the number of parts increases.
The prior art has another problem based upon the fact that the diameter of the adjustment bolt 18 is small. Hence, the strength of the threaded portion thereof with the adjustment nut 21 and the effective threaded area cannot be increased. This combination of factors may cause a breakage or a looseness due to vibrations.
A proposed prior art solution to this problem is to provide a caster in which the pinion gear 19 and adjustment bolt 18 are not used. In this case, however, another problem occurs in which the rotating operation of the handle becomes heavy and difficult.